Abstract
Human presence in natural environments is often a source of stress that is perceived by large ungulates as an increased risk of predation. Alternatively, disturbance induced by hikers creates a relatively predator‐free space that may serve as a refuge. We measured the behavioral responses of female caribou to disturbance associated with the presence of hikers during summer in the Gaspésie National Park. We used those data to determine whether caribou responded negatively to human activity (i.e., the predation risk hypothesis) or whether human activity resulted in a decrease in the magnitude of perceived risk (i.e., the refuge hypothesis). Female caribou with a calf spent nearly half of their time feeding, regardless of the presence of a trail or the number of hikers. They also decreased their vigilance near trails when the number of hikers increased. Conversely, lone females fed less frequently and almost doubled the time invested in vigilance under the same circumstances. However, both groups of females moved away from trails during the day, especially in the presence of hikers. We demonstrated that risk avoidance was specific to the maternal state of the individual. Lactating females accommodated the presence of hikers to increase time spent foraging and nutritional intake, providing support for the refuge hypothesis. Alternatively, lone females with lower energetic requirements and no maternal investment in a vulnerable calf appeared less tolerant to risk, consistent with the predation risk hypothesis. Synthesis and applications: Hikers influenced the vigilance–feeding trade‐off in caribou, underlining the importance of appropriate management of linear structures and human activities, especially across the critical habitat of endangered species. Even if some individuals seemed to benefit from human presence, this behavioral adaptation was not sufficient to reduce annual calf mortality associated with predation.
Highlights
Human disturbance can be an important driver of animal behavior (Ciuti et al, 2012; McLoed, Guay, Taysom, Robinson, & Weston, 2013)
We indicated the first date of each maternal state, by year, for all females followed during this study
Findings from other populations of Rangifer suggest that females with a calf incur a higher nutritional cost associated with gestation during the last trimester and milk production to support the dependent calf (Parker, Barboza, & Gillingham, 2009)
Summary
Human disturbance can be an important driver of animal behavior (Ciuti et al, 2012; McLoed, Guay, Taysom, Robinson, & Weston, 2013). Where nutritional intake is limited, lactating females might be more tolerant of human activities that reduce predation risk and increase foraging time (Lima & Bednekoff, 1999). According to the two main hypotheses that relate behavior to the trade-off between nutrition and risk, lactating females should tolerate low-risk disturbances and use human presence as a refuge against predation to reduce vigilance and increase the time spent foraging (i.e., the refuge hypothesis).
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